1. Field of the Invention
This invention relates to a method and an apparatus for controlling the torque which is transmitted from by a clutch engaged to an engine of a vehicle to a transmission when the vehicle is started from a stop.
2. Discussion of the Related Art
There are known a variety of methods for controlling the torque which is transmitted from a clutch to an engine of a vehicle. when the vehicle is started. The following are some examples thereof:
(1) A speed at which a clutch is engaged when the vehicle is started (i.e., increase of torque thereby transmitted) is controlled in proportion to a variation rate in the rotational speed of the engine (differential value), as disclosed in Japanese Published Unexamined Patent Application No. 39821/1983;
(2) An energizing current transmitted as torque by a powder clutch is controlled as an exponential function of the rotational speed of the engine when the vehicle is started, as disclosed in Japanese Published Unexamined Patent Application No. 15024/1982; and
(3) A clutch speed at which the control of a clutch is completed when the vehicle is started, that is, the rotational speed of the clutch at which the target engagement thereof is completed is set. Then, with the rotational speed at which the target engagement, of the clutch is completed, the torque transmitted from the clutch to a transmission is feed back controlled so that the clutch is actually engaged, as disclosed in Japanese Published Unexamined Application NO. 31532/1987.
These methods have their own advantages and make it possible to obtain satisfactory starting characteristics. However, it often that one as a feeling of physical disorder if he exchanges a vehicle equipped with a fluid coupling with one equipped with a clutch other than fluid coupling.
For example, one feels that the vehicle starts abruptly when the accelerator is operated or feel shocking when the vehicle is moved backward. This is because the characteristics of torque transmission by a fluid coupling which gives a feeling of a smooth sliding motion are slightly different from those characteristics obtained by the control methods as hereinabove stated at (1) to (3).
A driver who is used to the relatively rough operation of the accelerator which the fluid coupling permits has a feeling of physical disorder such as described above, if he drives the vehicle by operating the accelerator roughly with the same drive feeling as that in any type of vehicle in which the transmission of torque is controlled by any of the methods as hereinabove stated.